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Antique Radio Technical Forum
Freshman Works Great Topless

Posted by Norm Leal on 04/26/2009 10:20

Hi George

Sometimes the hum is there even outside the cabinet but not noticed. Putting a speaker in the cabinet can improve low frequency response

Try increasing electrolytic filter capacity to see if there is improvment.


:::Now that I have your attention. LOL I've been working on a Belmont 602B Freshman and it works great with the top off but when I put the top on (cabinet) it hums. Already tried goat shields but didn't ground them to the chassis. I know it is noise but having trouble correcting this problem. Anybody out there in radio land run into this problem? Thanks George T.
:: Try it with the tube shields grounded to chassis. Sometimes to leave the shield float like that may pick up hum. Also check if the cabinet is isolated from the chassis, and may even have a capacitor from chassis to cabinet.
:: Well I have tried pretty much everything with no luck. I'm kind of wondering if the speaker cloth might be causing it. The speaker cloth has what looks to be metal thread woven into it (gold). I sure would hate to take it all off and still have the problem. With the chassis playing with out the cabinet on it, it sounds fine but as you lower the cabinet onto the radio the hum gets louder. Weird!!!! Any ideas would be really welcome at this point. When you turn up the volume it covers up the hum. Thanks again, George.

Freshman Works Great Topless 
George T 04/23/2009 22:34 
Warren 04/24/2009 02:08 
George T 04/26/2009 00:50 
Norm Leal 04/26/2009 10:20 
George T ~ Norm / Warren 04/27/2009 21:35 
JF 04/28/2009 16:40 
George T 04/28/2009 22:03 

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